Method for blowing fine particles containing metal oxide into a reducing gas

ABSTRACT

According to a process for injecting metal-oxide-containing fine particles into a reducing gas, a central material stream formed by the fine particles and a carrier gas is introduced into the reducing gas and at least one gas stream formed by a secondary gas is directed against the material stream to ensure an optimum contact of the fine particles with the reducing gas, the gas stream atomizing the material stream and the fine particles being evenly distributed within the reducing gas.

BACKGROUND OF THE INVENTION

The invention relates to a process for injecting metal-oxide-containingfine particles into a reducing gas, as well as to an arrangement forcarrying out the process.

The process of introducing fine ore particles into a reducing gas ductand of reducing the ore particles during transport in the reducing gasduct is known (JP-A-62-164569). According to JP-A-62-164569, the fineore is sucked into the reducing gas stream via a nozzle. Herein, theproblem arises that the reducing gas cannot come into optimum contactwith the individual metal-oxide-containing fine particles.

The fine particles entering the reducing gas stream form a compactmaterial stream even if they are injected into the reducing gas streamby means of a carrier gas. Only after a certain distance has beencovered is the material stream fanned so that only a smaller distanceand, thus, only less time is available for reduction. Anotherdisadvantage is that the material stream, due to its compactnessresulting from its entering the space accommodating the reducing gas,may cause wearing of the wall delimiting said space by abrasion.

The object of the invention is to avoid these disadvantages anddifficulties and to solve the technical problem of creating a process ofthe type described above as well as an arrangement for carrying out theprocess allowing to ensure an optimum contact of the individual fineparticles with the reducing gas immediately after themetal-oxide-containing fine particles have entered a space accommodatingthe reducing gas so that each fine particle is enclosed by reducing gas,immediately after exiting the duct feeding the fine particles. This isto enable the chemical, physical and thermal reactions, which all takeplace starting from the surfaces of the fine particles, to proceedimmediately after introduction of the fine particles into the spaceaccommodating the reducing gas so that the time during which the fineparticles are staying in this space can be optimally used. This is alsoto allow a minimization of the arrangement for direct reduction and anoptimum utilization of the reducing gas.

SUMMARY OF THE INVENTION

According to the invention, this problem is solved by feeding a centralmaterial stream formed by the fine particles and a carrier gas into thereducing gas and by directing at least one gas stream formed by asecondary gas against the material stream, the gas stream atomizing thematerial stream and the fine particles being evenly distributed withinthe reducing gas.

The gas stream preferably imparts to the material stream a moment ofrotation about the axis of the material stream, the fine particles exitfrom the material stream by the centrifugal forces and the latter isdispersed.

The effect of utilizing the centrifugal forces can be even intensifiedby the gas stream imparting to the material stream periodicallyfluctuating moments of rotation, preferably of different dimensions,which also allows to find the optimum moment rotation.

The gas stream is expediently directed against the material stream askewand in such a manner as to intersect the material stream and onlypenetrates the outer zones of the material stream, angle α between thegas stream and the material stream being periodically variable.

The gas stream is advantageously formed by inert gas, but also areducing gas can be used therefor.

According to a preferred embodiment, the reducing gas flows past thematerial stream, i.e. the material stream is injected into a reducinggas stream, the material stream being expediently oriented in adirection opposite to the direction of flow of the reducing gas,preferably at an angle ranging between 100° and 160°.

Preferably, at least one gas stream is directed against the center ofthe material stream and penetrates the latter.

The process according to the invention can be particularlyadvantageously used for a reduction process characterized in that thematerial stream is fed into a reducing gas stream that departs from ameltdown gasifying zone in which a reducing gas containing CO and H₂ isformed by coal gasification and in which partially and/or completelyreduced metal-containing particles are completely reduced or melted,respectively, and said reducing gas stream, after the material streamhas entered, is subjected to solids separation and subsequently reactedin a reduction zone under reduction of a metal-oxide-containing ore, thefine particles separated during solids separation being supplied to themeltdown gasifying zone via a dust burner effecting an agglomeration ofthe fine particles.

An arrangement for carrying out the process according to the inventionis characterized by the combination of the following characteristicfeatures:

a space delimited by a wall for receiving a reducing gas,

an injection nozzle entering the space through the wall,

which is provided with a central pipe conducting fine particles and acarrier gas and,

at the mouth of the central pipe, is provided with at least one nozzleconnected to a gas duct for feeding a secondary gas, wherein

the longitudinal axis of the nozzle encloses an angle α with thelongitudinal center line of the central pipe, which ranges preferablybetween 20° and 60°.

According to a preferred embodiment, the longitudinal axis of the nozzleis oriented askew relative to the longitudinal center line of thecentral pipe, wherein, if the longitudinal axis of the nozzle isprojected perpendicularly onto a plane laid through the longitudinalcenter line of the central pipe and the nozzle mouth, an angle α rangingbetween 20° and 60° is formed between the projected longitudinal axis ofthe nozzle and the longitudinal center line of the central pipe.

In this arrangement, the nozzle is expediently movably arranged at themouth of the central pipe and, with its longitudinal axis, is capable ofassuming different positions, preferably different askew positions,relative to the longitudinal center line of the central pipe.

For atomizing the material stream, it may be advantageous under certainlocal circumstances if several nozzles are arranged only at one half ofthe circumference of the mouth of the central pipe.

For material streams of larger volumes, several nozzles are expedientlyarranged over the entire circumference of the mouth of the central pipein such as way as to be distributed approximately evenly.

A preferred variant is characterized in that the space for the reducinggas is formed by a pipe conducting the reducing gas, into which theinjection nozzle opens from the side, the longitudinal center line ofthe injection nozzle and the center line of the pipe conducting thereducing gas expediently including an angle ranging between 100° and160°.

The longitudinal axis of at least one nozzle preferably intersects thelongitudinal center line of the central pipe.

A preferred application of the arrangement according to the invention ischaracterized in that the arrangement opens into a gas discharge pipedeparting from a melter gasifier for melting and optionally completelyreducing metal ores as well as for producing a reducing gas containingCO and H₂ by coal gasification and the gas discharge pipe opens into asolids separator, such as a cyclone, from which the solids separated inthe solids separator can be recircled into the melter gasifier via asolids recircling duct and a dust burner.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1 shows a longitudinal section through an arrangement according tothe invention.

FIG. 2 shows a relevant cross section along line II—II of FIG. 1.

FIGS. 3, 4 and 5 schematically illustrate different embodiments of thearrangement according to the invention.

FIG. 6 shows the layout of an arrangement according to the invention ina plant for the direct reduction of fine ore.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the embodiment represented in FIGS. 1 and 2, thearrangement for injecting metal-oxide-containing fine particles into areducing gas is provided with injection nozzle 1 opening into space 3,which is penetrated by reducing gas, through wall 2. This space may beformed, for example, by a pipeline. Injection nozzle 1 is provided withcentral pipe 4 through which the fine particles are blown to its mouth 5by means of a carrier gas so that a material stream formed by the fineparticles is formed at the mouth.

At mouth 5 of central pipe 4, several nozzles 6 enclosing central pipe 4peripherally are provided which are connected to gas duct 7 for feedinga secondary gas, via gas conducting pipes 8 each. These gas conductingpipes 8 are designed as pipes arranged in parallel with longitudinalcenter line 9 of central pipe 4, which are provided in annular space 10enclosing central pipe 4 peripherally, into which space gas duct 7 runs.This annular space 10 is delimited by jacket 11 at the outside, which isclosed at the end face at mouth 5 and at the opposite end face by meansof end flanges 12, 13. Gas conducting pipes 8 can be turned in relationto end flanges 12, 13 by means of gastight bearings 14, 15.

The ends of gas conducting pipes 8 that are opposite to each other areclosed with flanges 16, 17. At outer flanges 17, pivots 18 are mounted,which project outwards. At pivots 18, drives for turning the gasconducting pipes around their longitudinal axes 19 are provided, whichare not represented in detail. At inside flanges 16 of gas conductingpipes 8, nozzles 6 are located whose axes 6′ enclose an angle α withlongitudinal center line 9 of the central pipe.

Gas conducting pipes 8 and, finally, nozzles 6 are supplied with gas viaannular space 10 and openings 20 of gas conducting pipes 8.

By turning gas conducting pipes 8 around their longitudinal axes 19, thegas streams flowing from nozzles 6 can be varied as to their position inrelation to the material stream in a way that the gas streams can bebrought from a position intersecting longitudinal center line 9 ofcentral pipe 4 into a position that is askew in relation to thislongitudinal center line.

A means for turning gas conducting pipes 8 around their longitudinalaxes 19 allows to periodically change the position of the gas streams inrelation to the material stream. Angle α enclosed by the gas streamswith longitudinal center line 9 of central pipe 4 ranges preferablybetween 20° and 60° and need not be equally large for all gas streams.

According to the embodiment represented in FIGS. 1 and 2, severalnozzles 6 are arranged over the entire circumference of mouth 5 ofcentral pipe 4 in such as way as to be distributed evenly. It maypossibly suffice if several nozzles 6 are arranged only at one half ofthe circumference of mouth 5 of the central pipe 4, as shown e.g. inFIGS. 4 and 5. This is especially the case if the reducing gas in space3 shows an intense directional flow.

It can be seen from FIGS. 3, 4 and 5 that the gas streams symbolized byarrows 21 are either oriented in a direction directly opposite tolongitudinal center line 9 of the central pipe (FIG. 5) or askew to it(FIGS. 3, 4), the material stream proper, with a minimum diametercorresponding to mouth 5, still being hit by the gas streams. The gasstreams thus impart to the material stream a rotation about itslongitudinal center line 9, the fine particles exit from the materialstream by the centrifugal forces and the latter is dispersed. Thisfunction occurs in addition to the atomizing effect caused by the gasstreams.

The gas streams are preferably formed by an inert gas. Inert gas mayalso be used as carrier gas. Instead of nozzles 6 also an annular gapcould be provided in end flange 12, through which a fan-shaped gasstream is directed against the material stream. If the position of thegas streams in relation to the material stream need not be changed, gasconducting pipes 8 are not required; in this case, nozzles 6 can berigidly inserted in end flange 12.

As shown in FIG. 6 below, the layout of the arrangement according to theinvention is described by a reducing gas discharge duct 23 conveying areducing gas from melter gasifier 22, in which a reducing gas containingCO and H₂ is formed in a meltdown gasifying zone by coal gasificationand reduced iron ore is melted, to a reduction vessel not represented.Both the reduction vessel in which ore is reduced and the meltergasifier can be designed, for example, as described in EP-A -0 576 414.

The reducing gas leaving melter gasifier 22 at opening 24 in dome region25 of melter gasifier 22 is supplied to cyclone 26 via reducing gasdischarge duct 23, in which cyclone the particles entrained by thereducing gas are separated.

In the starting region of reducing gas discharge duct 23, cooling gas isfed into the reducing gas via gas feeding means 27 in order to cool thereducing gas to the temperature required for reduction in the reductionvessel. Injection nozzle 1 according to the invention is located shortlythereafter, longitudinal center line 9 of central pipe 4 being orientedin a direction opposite to the direction of flow of the reducing gas andforming an angle between 100° and 160° with it.

The iron ore injected into the reducing gas and finely distributed inthe latter immediately after entering into the reducing gas dischargeduct is reduced, at least partially reduced, within reducing gasdischarge duct 23 and separated in cyclone 26. The at least partiallyreduced iron ore is supplied via dust bins 27 and injector 28 operatedpreferably with nitrogen gas to dust burner 29 located at a side wall ofmelter gasifier 22. Dust burner 29 effects an agglomeration of the fineparticles and optionally also complete reduction.

Additionally to iron ore also fine-grained metallurgical wastes orrecyclings in oxidized and/or metallic form as well as possiblyadditionally carbon-containing materials can be charged via thearrangement according to the invention.

The arrangement according to invention allows to replace 15 to 30% ofthe ore by fine ore and/or metallurgical dusts, etc., which may also bemixed with contaminants.

What is claimed is:
 1. A process for injecting metal-oxide-bearing fineparticles into a reducing gas stream conveyed by a reducing gas line,characterized in that a central material stream formed by the fineparticles and a carrier gas is introduced into the reducing gas streamand the reducing gas flows toward the material stream, the materialstream being oriented in a direction opposite to the direction of flowof the reducing gas, and at least one gas stream formed by a secondarygas is directed against the material stream, with the gas streamdispersing the material stream and the fine particles being evenlydistributed within the reducing gas stream.
 2. A process according toclaim 1, characterized in that the gas stream imparts to the materialstream a moment of rotation about the axis of the material stream, anddue to the centrifugal forces the fine particles exit from the materialstream and the latter is dispersed.
 3. A process according to claim 2,characterized in that the gas stream imparts moments of rotation to thematerial stream in a periodically fluctuating manner.
 4. A processaccording to claim 2, characterized in that the gas stream is directedagainst the material stream askew and in such a manner as to intersectthe material stream and only penetrates the outer zones of the materialstream.
 5. A process according to claim 4, characterized in that theangle (α) between the gas stream and the material stream is variedperiodically.
 6. A process according to claim 1, characterized in thatthe gas stream is formed by inert gas.
 7. A process according to claim1, characterized in that at least one gas gas stream is directed againstthe center of the material stream and penetrates the latter.
 8. Aprocess according to claim 1, characterized in that the material streamis fed into a reducing gas stream that exits from a meltdown gasifyingzone in which a reducing gas containing CO and H₂ is formed by coalgasification and partially and/or completely reduced metal containingparticles are completely reduced or melted, respectively, and saidreducing gas stream is subjected to solids separation after the materialstream has entered and subsequently is reacted in a reduction zone byreduction of a metal-oxide-containing ore, the fine particles separatedduring solids separation being supplied to the meltdown gasifying zonevia a dust burner (29) effecting an agglomeration of the fine particles.9. An arrangement for carrying out the process according to claim 1,characterized by the combination of the following characteristicfeatures: a space (3) for receiving a reducing gas delimited by a wall(2, 23), an injection nozzle (1) for injecting a material stream, saidinjection nozzle entering the space (3) through the wall (2, 23),provided with a central pipe (4) for conducting fine particles and acarrier gas and at least one nozzle (6) connected to a gas duct (7) forfeeding a secondary gas at the mouth (5) of the central pipe (4), thelongitudinal axis (6′) of the nozzle (6) and the longitudinal centerline (9) of the central pipe (4) including an angle (α), said angle αbeing such that the material stream is oriented opposite to thedirection of flow of the reducing gas.
 10. An arrangement according toclaim 9, characterized in that the angle (α) ranges between 20° and 60°.11. An arrangement according to claim 9, characterized in that thelongitudinal axis (6′) of the nozzle (6) is oriented askew relative tothe longitudinal center line (9) of the central pipe (4), wherein, ifthe longitudinal axis (6′) of the nozzle (6) is projectedperpendicularly onto a plane laid through the longitudinal center line(9) of the central pipe (4) and the nozzle mouth, an angle (α ) rangingbetween 20° and 60° is formed between the projected longitudinal axis(6′) of the nozzle (6) and the longitudinal center line (9) of thecentral pipe (4).
 12. An arrangement as claimed in claim 9,characterized in that the nozzle (6) is movably arranged at the mouth(5) of the central pipe (4) and with its longitudinal axis (6′) iscapable of assuming different positions relative to the longitudinalcenter line (9) of the central pipe (4).
 13. An arrangement accordingclaim 9, characterized in that several nozzles (6) are arranged only atone half of the circumference of the mouth (5) of the central pipe (4).14. An arrangement according to claim 9, characterized in that severalnozzles (6) are arranged over the entire circumference of the mouth (5)of the central pipe (4) in such a way as to be distributed approximatelyevenly.
 15. An arrangement according to claim 9, characterized in thatthe longitudinal center line (9) of the injection nozzle (1) and theaxis of the pipe (23) conveying the reducing gas include an angleranging between 100° and 160°.
 16. An arrangement according to claim 9,characterized in that the longitudinal axis (6′) of at least one nozzle(6) intersects the longitudinal center line (9) of the central pipe (4).17. An arrangement according to claims 9, characterized in that thearrangement opens into a gas discharge pipe (23) departing from a meltergasifier (22) for melting and optionally completely reducing metal oresas well as for producing a reducing gas containing CO and H₂ by coalgasification and the gas discharge pipe (23) opens into a solidsseperator (26), such as a cyclone, from which the solids separated inthe solids seperator (26) via a solids recircling duct and a dust burner(29) can be recircled into the melter gasifier (22).
 18. A processaccording to claim 3, wherein the moments of rotation are of differentdimensions.
 19. A process according to claim 1, wherein the materialsteam is oriented at an angle between 100° and 160° opposite to thedirection of flow of the reduction gas.
 20. An arrangement as claimed inclaim 12, wherein said longitudinal axis (6) is capable of assumingaskew positions relative to the longitudinal center line (9) of thecentral pipe (4).